Conventionally, a motor vehicle has a plurality of safe driving assist systems which are mounted thereon and include a lane keeping assist system and/or an automated cruise system. In such systems, an automatic brake control and/or a steering assist control or the like are used respectively. Therefore, respective ones of a brake request signal for performing the automatic brake control, and a steering request signal for performing the steering assist control may be issued from respective ones of the systems. For example, the brake request signal may be issued from different systems at different timings. In such case, one of the request signals in the plurality of request signals may be prioritized over the others in the plurality of request signals (for example, refer to Patent Document 1).